The present invention relates to a coating material comprising at least one binder and at least one photocatalytically active particle, to a process for producing this coating material and to the use of this coating material.
Coating materials comprising photocatalytically active particles are already known from the prior art.
JP 11 181339 A discloses a hydrophilic coating for metals, polymers, concrete, comprising photocatalytically active titanium dioxide particles. The titanium dioxide particles described in JP 11 181339 A have a particle diameter of 1 to 100 nm, comprise particles of SnO2 and are silica and/or silicone coated. The layer thickness of this coating of silica and/or silicone is not disclosed. The coating material prevents soiling of a surface coated with this material. A surface thus treated further has self-cleaning properties when rained upon. Therefore, the coating materials described in JP 11 181339 A are suitable for coating surfaces of buildings, window frames and other goods.
JP 2006-18 14 90 discloses a coating method for coating materials. A photocatalyst consisting of titanium dioxide, zirconium dioxide, zinc oxide, tin oxide, cerium oxide, antimony oxide, indium oxide doped with tin, tin oxide doped with antimony is applied with a nonaqueous solvent to the surfaces to be protected. In a preferred embodiment, a photocatalyst consisting of titanium dioxide is coated with ceramics such as apatite, silica, activated carbon, activated alumina or porous glass to secure the photocatalyst to the surface to be treated. The process described in this document is complicated by the necessity of having to apply at least two layers.
JP 2006-233343 discloses a liquid photocatalyst composition for coating textiles which comprise photocatalyst particles having a preset particle diameter and a coating. The size of these photocatalyst particles is 0.5 to 10 μm. In a preferred embodiment, the core of the photocatalyst particle consists of titanium dioxide and the envelope consists of silica. Envelope thickness and porosity are not disclosed for the photocatalytically active particle.
JP 11228873 A discloses a paint composition comprising titanium dioxide particles coated with porous silica and having photocatalytic properties. The composition further comprises titanium dioxide pigment and an organic resin binder. JP 11228873 A does not disclose the particle diameters of the photocatalytically active particles or the thickness of the silica layer.
WO 2005/100459 A1 discloses a coating material comprising a binder and at least one filler comprising particles having a size and/or surface roughness of 100 μm or less and also a catalytically active agent, the binder being at least partly degraded by the photocatalytic effect and a microstructured, self-cleaning surface is formed. The photocatalytically active agent used in WO 2005/100459 is an oxide of titanium, zinc, iron, manganese, molybdenum and/or tungsten, which comprises at least one additive selected from C, N, S and/or from a transition metal oxide and/or transition metal halide. WO 2005/100459 A1 does not disclose the particle size of the photocatalytically active particles.
Prior art coating materials comprise photocatalytically active particles having the disadvantage that not just the soils present on the coating material in use are photocatalytically degraded, which is desired, but also the binder present in the coating material. This is not desired and the photocatalytic destruction of the organic matrices described in the prior art lower the photoactivity of the surface produced. Not only the photoactivity but also the durability or resistance of the coating materials according to the prior art is inadequate as a result.